Tamper proof electrical connector



Feb. 6, 1962 E. c. QUACKENBUSH 3,020,513

TAMPER PROOF ELECTRICAL CONNECTOR Filed Feb. 3, 1958 FIG.4

INVENTOR. Edward Clarke Quockenbush ATTORNEYS a corporation of Connecticut Filed Feb. 3, 1958, Ser. No. 712,846 4 Claims. '(Cl. 339-91) This invention relates to electrical terminal connections and in particular provides a tamper proof electrical connector suitable for installation in exposed positions, specifically the connector of this invention includes a receptacle for fixed emplacement against the surface of a wall or the like and a plug for mating with the receptacle which are provided with a latching device which in mated position of the plug and receptacle is enclosed and which can be released only by employment of a suitable tool.

In many subscriber telephone installations the telephone set is connected by an unsupported cable to a terminal block affixed to the surface of an adjacent wall or baseboard located at the end of a cable of secured telephone lines and in which suitable connections are made between the secured lines and the free lines leading to the telephone set. Customarily the terminal block is covered by a small metal case which is held in position by a screw passed through its center. Such installations are readily accessible to unauthorized tampering which permits the installation of unauthorized equipment and which can lead tomalfunctioning of the telephone.

It is an important object of this invention to provide a device for replacing such terminal blocks which permits installation of subscriber telephone equipment without the services of a trained technician and which once installed is foolproof and not readily disconnected. It is a further object of this invention to provide such a device having a simple construction which can be fabricated with minimum thickness and size and in which the necessary terminal connections can be made in a simple manner.

It is still a further object of this invention to provide such a device including a latching plug and socket connection which is simple for an uninstructed and untrained person to install, but which once installed is permanently emplaced and cannot be readily opened without the services of a trained technician provided with a proper opening tool and a knowledge of the functioning of the latching arrangement.

These and other objects of this invention which will become apparent hereinafter are generally obtained by providing a receptacle for fixed emplacement against the surface of a wall, baseboard or the like and containing contact members which are ordinarily connected to the secured telephone lines, and by providing a plug for mating with the receptacle and containing contacts similarly connected to the unsecured conductors leading to the telephone set. Preferably the contacts areof the axially mating type, i.e., pin and socket type contacts, and in any event are engaged when the plug and receptacle abut in a mating position.

The receptacle member is provided with a projection on its mating side which is spaced above the surface of the wall or baseboard on which the receptacle is installed but which is adjacent to and below the contacts in the receptacle. The plug has its underside stepped such that a thin or stepped portion of the plug which carries the contacts fits over the projection on the receptacle in mated position, thus forming polarizing means which permits mating engagement in one position only. A latch in the form of a spring arm mounted on the plug and spaced beneath the underside of the stepped portion of the plug slides beneath and engages the underside of the projection on the receptacle in mated position, to provide positive States mm:

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interlocking means for holding the plug and receptacle in mating contact engagement. The spring arm is released by pushing it toward the wall or baseboard'to disengage the spring arm and projection, and a pair of openings are provided, one in the stepped portion of the plug andone in the projection on the receptacle, which register in mating position of plug and receptacle and which are aligned with the spring arm, thus forming akeyway common to the engaged plug and receptacle, to facilitate insertion of a special tool through theopenings to disengage the spring arm and permit opening of the plug and receptacle.

In order to prevent unauthorized tampering the side walls of both plug and receptacle adjacent to their abutting portions cooperate together with the surface of the wall or baseboard on which the receptacle is installed substantially to enclose the space beneath the underside of the projection on the receptacle when-in mating position.

Preferably the side walls of the receptacle are stepped down from the main body of the receptacle to the level of the projection and extend along the 'sides of t e projection spaced apart a sufiicient distance to receive the opposite sides of the spring arm thereby providing a guide for proper axial. mating of the contact members and at the same time providing a pair of relatively thick ears abutting the surface of the wall or baseboard on each side of the projection through which screws or other fastening devices for installing the receptacle to the wall or baseboard can be passed. The fastening devices are thus hidden in mating position by the stepped portion of the plug, thereby further preventing unauthorized removal of the device.

Preferably the receptacle body which ordinarily is constructed of a block of rigid dielectric material, such as a phenolic resin, is hollowed from its underside and' contains a terminal connecting device associated with each contact in the receptacle, thus facilitating connection of the secured telephone lines to the receptacle contacts. In such case a receptacle block will ordinarily include closed side walls and top, such that when placed against the wall the open underside of the receptacle is effectively closed to prevent unauthorized tampering with the terminal connections.

For a more complete understanding of the practical application of the principles of this invention reference is made to the appended drawings in which:

FIGURE 1 is a partially sectioned elevation of a plug and receptacle installation according to this invention;

FIGURE 2 is a side view of the device shown in FIG- URE l; 7

FIGURE 3 is a rear view of the device shown in FIG- URE l;

FIGURE 4 is a vertical section taken at line 4-4 in FIGURE 3; and

FIGURE 5 is an isometric view of a portion of the device shown in FIGURES 1-4.

Referring to the drawings the tamper proof receptacle and plug construction of this invention basically includes a receptacle 10, which in the illustrated case is shown affixed to a wall board 11, and a plug 12.

Receptacle 10 is constructed of a rigid dielectric block 13 which functions both as a receptacle housing and a terminal block. Block 13 is generally hollowed from its underside 14 and has a closed side Wall including a rear portion 15 in which is provided an aperture 16 adjacent to underside 14. At the opposite endof block 15 the side wall includes a fiat portion 17 through which a series of four parallel and equally spaced openings 18 extend to the hollow interior 19 of block 13. Openings 18 are spaced across side wall 17 and are located adjacent to the top 26 of block 13. The interior 19 of block 13 is closed except through the underside 14 of block 13 by the remaining portions 21 and 22 of the side wall of block .13 which extend between side wall portions and 17.

In its interior 19 block 13 also includes four integral terminal posts 23, which depend from top 20, one such post 23 being aligned with each opening 18 in side wall portion 17 and carries a contact 24, the engaging parts 25 of which are positioned in the associated opening 18 and which is secured to the associated terminal post 23 by means of a screw 26. Ordinarily, the end of a Secured telephone cable 27 is brought through opening 16 into interior 19 of block 13 and the separate conductors in cable 27, in a conventional manner, are appropriately separated to connect with two or more of terminal posts 23. Appropriately the ends of the separate conductors in cable 27, in a conventional manner, are provided with terminal lugs which are received between screws 26 and contacts 24.

Referring more particularly to FIGURE 5, which shows an individual contact 24, it will be observed that contact 24 includes a flat shank 28, which at one end is provided with an opening 29 for receiving screw 26 and from the sides of the other end of which are extended the working parts 25 for making axial connection with a telephone jack type, pin contact member.

Receptacle 10 is further provided with an integral extension of block 13 in the form of a shelf, i.e., projection 30, which is centrally located on side wall portion 17 with its underside 31 spaced above the level of the underside 14 of block 13 and with its upper side 32 adjacent to and below openings 18. Projection is enclosed on each side by extensions of side walls 21, 22 in the form of cars 33, 34 respectively, the upper surfaces of which are contiguous with the top 32 of projection 30 and the undersurfaces of which are contiguous with the underside 14 of block 13. Each car 33, 34 is suitably provided with a transverse bore 35 which extends through block 13 for receiving screws or other suitable fastening devices by which receptacle 10 can be secured to the surface of a wall, baseboard or the like. Projection 30 is also provided centrally between cars 33, 34 adjacent side wall 17 with a transverse bore 36 and is provided on its under surface 31 centrally between cars 33, 34 and its end remote from side wall 17 with a short cylindrical stud 37 which is beveled as indicated by the reference numeral 38 adjacent the end of projection 30 remote from side wall 17.

Plug 12 is similarly constructed of a rigid dielectric block 40, but which is divided transversely into an upper shell 40a and the lower shell 40b. The underside of lower shell 40b includes an upwardly stepped portion 41 at one end of block 40, such that there is a rearward projection, i.e., boss-42 at the other end of block 40. Upper shell 40a is closed at its top 43 and along its sides meets the sides of lower shell 4%, such that a continuous side wall encloses the mated shells 40a and 40b.

A portion 44 of the side wall at the end of stepped portion 41 is flat and has a size suitable for abutting side wall portion 17 of block 13 above projection 30. Complementary apertures at the meeting edges of shells 40a and 40b alongside wall portion 44 define four bores 45, which are spaced at intervals such that bores 45 are aligned with openings 18 in side wall portion 17 when side wall portions 17 and 44 abut and stepped portion 41 of block 40 overlies projection 30 on block 13. Similarly in the portion 46 of the side wall of block 40 remote from the abutting side wall portion 44 shells 40a and 40b are apertured to define another opening 47 between them.

lnteriorly, shells 43a and 4811 are hollowed to form a chamber 48 into which bores 45 and opening 47 lead. Each of the bores 45 is enlarged at 49 intermediate of 4 its length and receives a telephone tube type, pin contact member 50 which suitably has an enlarged portion received in the enlarged portion 49 of bore 45. The tips 51 of contact members 50 extend parallel to each other forwardly of side wall portion 44 and are aligned with contact members 24 in receptacle 10 for axial mating with such contact members. The end of unsecured telephone cable 52 including conventionally four separately insulated conductors 53 leading for example to a telephone set is introduced through opening 47 into the interior 48 of block 40 with each conductor 53 electrically and mechanically connected at its interior end to a separate contact member 50. Suitable strain relief is provided by knotting cable 52 within interior 48 of block 40 or by providing a metal clip 52a over the end of cable 52 Within block 40 as illustrated in FIGURE 4.

On its underside boss 42 is recessed as indicated by the reference numeral 54 and carries the head end of a T-shaped, fiat spring arm 55, the other end of which extends spaced beneath the underside of stepped portion 41 toward side wall portion 44. Spring arm 55 is secured by means of screws 56, 56 at its head end to lower shell 40b. Preferably screws 56, 56 also threadedly engage upper shell 40a thus holding the two shells rigidly together. Adjacent to boss 42, where spring arm 55 extends out over the underside of stepped portion 41 of block 40, spring arm 55 is centrally apertured as indicated by the reference numeral 57, and the end of spring arm 55 remote from boss 42 and adjacent to side wall portion 44 is slightly bent away from the underside of stepped portion 41 as indicated by the reference numeral 58.

The construction of plug 12 is completed by a transverse opening 59 extending through both shells 40a and 4312 between the middle pair of contact members 50 and which is aligned with, but of less diameter than opening '36 in projection 39 of receptacle 10.

In installation, the end of secured telephone line 27 is laid in aperture 16 with the ends of its various separately insulated conductors secured on the appropriate terminal posts 23'by means of screws 26. Thereafter receptacle 10 is placed with it's underside 14 against the surface of baseboard 11 and fixed in position by means of wood screws 60, which are extended through bores 35, 35 in ears 33, 34 into baseboard 11 to hold the underside 14 of receptacle 10 upon the surface of baseboard 11. The hollow interior 19 of block 13 is thereby enclosed except for openings 16 and 18, and the space'beneath projection 30 is thereby enclosed by the side wall extensions 33, 34 except for an opening at the end of projection 30 remote from side wall 17.

To complete installation plug 12, suitably connected to a telephone set bycable 52, is advanced with its side wall portion 44 leading toward side wall portion 17 of receptacle 10 and with spring arm 55 on its underside adjacent to the surface of baseboard 11. As plug 12 is thus advanced spring arm 55 is inserted beneath the underside 31 of projection 30 with its curved tip 58 riding across beveled surface 38 of stud 37 and with stepped portion 41 riding above the upper surface 32 of projection 30. As plug 12 is further advanced spring arm 55 is forced down bythe camming action of surface 38 causing spring arm 55 to ride understud 37 and snap back into position receiving stud 37 in aperture57. Simultaneously the tips 51 of phone plug contactmembers 50 enter apertures 18 and engage the working parts 25 of their associated socket contacts 24 with side wall portion 44 abutting side wall portion 17.

As will be evident, plug 12 and receptacle 10 are then engaged with their respective side walls adjacent to side walls 17 and 44rneeting tightly, forming a joint together with the surface of baseboard 11 which substantially encloses. the space beneath the underside 31 of projection 30 and henceprevents release of engagement of spring arm 55 at stud 37 by the use of any ordinarily available tools.

Bore 5 and bore 36, however, are in registry and aligned with the outer end of spring arm 55. Thus by insertion of a tool T through bores 59 and 36, spring arm 55 can be depressed lifting it away from stud 37 to release engagement of plug and receptacle. As indicated in the drawings the diameter of bore 59 is somewhat smaller than the diameter of bore 36 thus permitting a small relative axial movement between plug and receptacle 12 with tool T inserted in vhich the apertured portion 57 of spring arm 55 can be held away from stud 37 sufiiciently to prevent its re-engagement with stud '37 subsequent to removal of tool T.

From the preceding description it will be apparent that many modifications of the arrangement described in the drawings are possible, It will be apparent that the pin contact and socket contact can be interchanged between movable plug and fixed receptacle. The enclosure of the under surface of projection 30 can be accomplished as readily by extended side wall portions on plug 40 in place of those on receptacle block 13. It will be, moreover, apparent that in practice the tool T may have specially keyed shapes for which the transverse dimensions of bores 59 and 36 can be specially designed in order to prevent opening of the plug and receptacle by means of any ordinary shaft.

The claims:

1. A tamper-proof electrical connector adapted to be rigidly mounted upon a support surface comprising, in combination, a contact receptacle and a mating contact plug with at least one coacting set of electrical contact members respectively aflixed to said receptacle and said plug and disposed for mating engagement, said contact receptacle having a shelf projection intermediate its top and bottom portion with transverse bores therein through which retaining means may be inserted for rigidly mounting said contact receptacle to said support surface, said contact plug having a stepped configuration mating to said shelf whereby said bores are covered when said plug is in mating engagement with said receptacle, a spring arm aifixed to said plug, a projection on the undersurface of said shelf for locking engagement with said spring arm, and matching transverse openings in said receptacle and plug in substantial axial alignment when said receptacle and plug are in mating engagement whereby upon insertion of a tool in said aligned openings said spring arm is released from said projection.

2. The tamper-proof electrical connector of claim 1, wherein said coacting set of electrical contact members surface spaced from the bottom of said receptacle and containing transverse bores into which retaining means may be inserted for rigidly mounting said receptacle to said plane surface, said contact plug having a stepped configuration mating to said shelf whereby said bores are covered when said plug is in mating engagement with said receptacle to form the block configuration of the total connector, a spring arm aifixed to said plug and so disposed thereon that it will enter the space beneath said shelf projection when said contact receptacle is mounted on a plane surface, a projection on the undersurface of said shelf for locking engagement with said spring arm, and matching transverse openings in said receptacle and plug in substantial axial alignment when said receptacle and plug are in mating engagement whereby upon insertion of a tool in said aligned openings said spring arm is 7 released from said projection.

4. The combination of claim 1 further defined in that the innermost of said transverse openings is the larger of said openings, said aligned openings allowing for entrance of a tool whereby said spring arm may be disengaged from said projection, and said larger opening providing leeway so that said receptacle and plug may be moved partially apart to keep said spring arm and said locking projection disengaged while said tool is removed from said openings.

References Cited in the file of this patent UNITED STATES PATENTS 846,246 Prather Mar. 5, 1907 1,897,954 DOlier Feb. 14, 1933 1,967,021 Gary July 17, 1934 2,113,687 Grace Apr. 12, 1938 2,183,651 Langston et al Dec. 19, 1939 2,688,123 Benham et a1. Aug. 31, 1954 2,838,738 Winkler June 10, 1958 

